[e2e] Packet reordering in Internet

[slblake@petri-meat.com]

On Tue, 25 Aug 2009 15:39:56 +0200, Detlef Bosau <detlef.bosau at web.de>
wrote:

> Per Hurtig (work) wrote:
>> I know that TCP is sorting incoming packets, I should have specified
>> my question better :) What I was wondering is if packets are more
>> likely to be reordered in data centers than in the regular Internet,
>> due to the specific architecture of data centers.
>>
>> For instance, I've seen papers that argue that packet reordering is
>> more prevalent in high-speed environments, e.g. [1], and data centers
>> would likely belong to this type of environment.
>>
>> [1] "Packet reordering in high-speed networks and its impact on
>> high-speed TCP variants". Feng, Jie and Ouyang, Zhipeng and Xu, Lisong
>> and Ramamurthy, Byrav. In Computer Communications 32(1), pp. 62-68,
>> January 2009.
>>
>>   
> 
> Unfortunately, I did not yet read this paper. However, I don't think 
> that a high network throughput alone will cause packet reordering. 
> Nevertheless, excessive traffic shaping using numerous buffers, token 
> buckets and leaky buckets may lead
> to packet reordering. I still do not really know, e.g., how things like 
> "committed information rate" and the like are implemented in Frame 
> Relay, so it could be worthwhile to have a look at these things in 
> practical networks.

Assuming stable paths, the only thing that should result in re-ordered
packets within a TCP connection is broken load balancing (inside packet
switches and between them).  Properly implemented metering, queueing, and
scheduling do not result in re-ordering.


Regards,

// Steve